Monday, February 27, 2006

Linux: Testing your iptables firewall

I have an old Pentium II running Debian Testing to protect my internal network from the Internet. Yesterday, I decided to test this firewall using a site that performs a portscan. I came accross http://www.testmyfirewall.com/ that did exactly what I wanted. This site claimed my internal address (the address of the computer sitting behind the firewall) was exposed to the outside. Yeah, right. After some digging I came accross this post from a guy having the same "problem". It seems that testmyfirewall starts an applet displaying the address of the computer running the applet, which is indeed the one sitting behind the firewall.
So this site does not test your firewall, it only tests your browser which is a different thing.
Just be aware of sites that claim to test your firewall, they're not allways right.

2 comments:

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Alex said...

To really test your firewall:

https://www.grc.com/x/ne.dll?bh0bkyd2

http://www.grc.com is furthermore a very nice supplier of information and tools regarding network security...

(dit even in het engels, wellicht dat er anderen hier bij gebaat zijn ;-). Azalin.)